In the modern plasma display panels (hereinafter referred to as PDPS), those of the type in which two pieces of substrates are laminated one upon the other maintaining a suitable gap, the periphery thereof is sealed with glass to constitute a housing and the gap is filled with a gas so that the panel is flat. Of the two pieces of substrates, the front plate must be composed of a glass plate and the other back plate is also composed of a glass plate of the same kind since it is inexpensive. Therefore, the following description deals with the PDP of this type.
In producing the PDPS, the air is exhausted prior to filling with a gas causing the pressure differential to become the greatest between the inside and the outside of the housing. Due to this pressure differential, the two pieces of glass substrates undergo a deformation. The deformation further increases due to the heating that is effected to release the gas that is adsorbed in the housing. In order to suppress the deformation to a negligible degree, the thickness of the glass plates must be increased or the size of the panel must be decreased. Such a limitation can be removed if spacers are provided between the two pieces of glass plates; i.e., spacers are indispensable for large display panels.
In the PDPs in which a plurality of discharge cells are arranged, furthermore, diaphragms or spacers are usually necessary to maintain a suitable gap for electric discharge or to prevent crosstalk relative to the neighboring cells irrespective of the type of electric discharge such as the AC type or the DC type.
Here, the arrangement of discharge cells in the PDP is determined depending upon the object of its use, and examples include a figure-eight display consisting of seven segments, a character display consisting of 5.times.7 dots, a full-dot display consisting of 640.times.480 dots, and the like.
FIGS. 1 to 5 illustrate arrangements of discharge cells in the PDPs, and wherein reference numeral 1 denotes a front glass plate, 3 denotes a diaphragm, 5 denotes a back glass plate, 6 denotes positive electrodes, and reference numeral 7 denotes negative electrodes. As shown in these drawings, there are used diaphragms and spacers (hereinafter often referred to simply as diaphragms) having a variety of shapes and cell holes of a variety of arrangements. The diaphragm can be prepared by the same method for any arrangement of cells, and a variety of methods have heretofore been attempted such as:
Method A: Thick-film method (multi-layer printing by screen printing), PA1 Method B: Etching of photosensitive sheet glass, and PA1 Method C: Machining of sheet glass.
Among them, the method A is excellent in regard to economy and mass-produceability but has a defect in that a gap large enough for electric discharge is not obtained unless the printing is repeated many times. In the full-dot display PDP, in particular, making the dot pitch very fine (e.g., 0.2 mm of dot pitch) is very important but cannot be accomplished by the screen-printing method. A fine dot pitch was accomplished in the shape of stripes as shown in FIG. 2 (Y. Amano: SID Int. Symp. Dig. Tech. Paper, p. 160, 1982), which, however, cannot be applied to diaphragms that completely surround the discharge cells as shown in FIGS. 1 and 4, and is not practical since it requires a very high degree of technology.
There is a great difference in sense between the case where the discharge cells are completely surrounded by the diaphragm (hereinafter referred to as the completely closed diaphragm) as described above and the case where the diaphragm does not exist relative to the neighboring cells even in one direction (hereinafter referred to as incompletely closed diaphragm) like that of the shape of stripes.
For instance, when a luminous color of a rare gas itself is to be utilized such as a PDP of an orange luminous color by the electric discharge of a neon gas, even the incompletely closed diaphragm can be put into practical use since the emission of light is limited to the proximity of electrodes of the selected cell. As the gap among the light-emitting cells becomes small, however, the electric discharge tends to take place among the neighboring cells. In the case of a multi-color or a full-color PDP, furthermore, the light is emitted by exciting the fluorescent material using ultraviolet rays produced by the electric discharge. When the incompletely closed diaphragm is used, therefore, the ultraviolet rays leak causing the fluorescent material of the neighboring cells to be excited and resulting in the emission of light. That is, the crosstalk or the color blurring develops inevitably to impair the color reproduceability and resolution, and the display panel loses its value. In regard to these points, therefore, the method A is not suited for preparing a highly fine and completely closed diaphragm, and is no practical for realizing the color PDP.
It is considered that the method B makes it relatively easy to accomplish the display panel maintaining high accuracy using, however, a very special photosensitive glass having the disadvantage of cost and economy. Moreover, fabricating a glass sheet which is as thin as 0.1 to 0.5 mm is not practical since the glass becomes brittle.
In the case of the method C, difficulty is involved in machining highly fine cell pitches and difficulty is involved, too, in the assembling operation, though there can be used a general glass.
So far, therefore, there has not yet been provided a diaphragm or a spacer that can meet the production of PDPs maintaining high accuracy, that can maintain a suitable space for electric discharge, and that can be mass-produced relatively cheaply.
The present invention was achieved in view of the above-mentioned problems inherent in the prior art, and its object is to provide a PDP which satisfies the demand for high accuracy and which is excellent in economy and mass-produceability.